Structure and rheology of polypropylene with various architectures prepared by coagent‐assisted radical processing

Abstract

AbstractThe grafting of polar monomers to polyolefin backbones carried out in the melt in the presence of peroxides is accompanied by a restructuring of the pristine macromolecule architecture depending on reaction conditions and original polyolefin structure. In the case of polypropylene (PP), side reactions, mainly degradation, are often controlled by the use of coagents which also provide a more complex scenario as far as possible reactions and final polymer structure are concerned. We have demonstrated that 2‐furyl acrylates are very active in maintaining the high molecular weight of PP during various functionalization processes carried out in the melt in the presence of peroxides. In the study reported here, PP samples modified in the melt by free radical processes initiated with peroxides in the presence of butyl‐3‐(2‐furyl) propenoate and its mixture with maleic anhydride were examined, and the effect of structural changes achieved were related to the rheology of the melt and morphological behaviour under heating. Rheological analysis is consistent with the formation of long branched macromolecules to an increasing extent with increasing content of reagents with respect to the polyolefin. Differential scanning calorimetry shows that the amount of long‐chain branching is responsible for a decrease of the melting temperature and an increase of the crystallization temperature. These results confirm that the functionalization coagent and monomer can give large macromolecule structure changes which can be driven in different directions depending on feed composition. Copyright © 2010 Society of Chemical Industry